David Davis, McKee v. United States (75 U.S. 163…
“ It is a familiar principle of public law, that unlicensed business intercourse with an enemy during a time of war is not permitted. Congress, therefore, in recognition of this principle, when it declared, on the 13th day of July, 1861, that commercial intercourse between the seceding States and the rest of the United States should cease and be unlawful, after the proclamation of the President that a state of insurrection existed, authorized the President, in his discretion, to license trade. ”
